1. Field of the Invention
The invention relates to the modification of polyols by the addition of epoxy resin and, more particularly, relates to the addition of epoxy resins to amines and polyol initiators to produce modified polyols suitable for use in improved rigid polyurethane foams.
2. Description of the Prior Art
Presently, amino polyols suitable for use in rigid foams are made by the reaction of sucrose and an amine with mixtures of alkylene oxides. Persons skilled in the art of making polyols can add alkylene oxides to polyhydric initiators such as sucrose, methylglucoside, sorbitol, etc. and mixtures of these products with aliphatic or aromatic amines to prepare products in the 350-650 hydroxyl number range. While generally satisfactory, foam prepared from these prior art polyols have poor dimensional stability at low temperature and a low heat distortion temperature. Conventional means of improving these properties by use of a higher functionality initiator or short chain crosslinkers lead to high viscosity materials which are hard to process and show poor compatability with isocyanates. Therefore, it is an object of this invention to increase the functionality of polyols such as sucrose amino polyols by their reaction with epoxy resins to prepare a new type of polyether polyol which would produce improved rigid foams.
Other patents disclose reactions involving polyols and epoxy resins. Japanese Pat. No. 71-24,255 concerns the reaction of a glycerine-based 3,000 molecular weight triol with 2% Bisphenol A epoxy resin to produce foams with increased hardness. A close examination of this patent will show that the epoxy resin is added at the end of the triol chain. Those skilled in the art of making polyols would expect that this technique could not be used in making polyols for rigid foams. Such polyols are very high in functionality and one would expect a high degree of crosslinking which would result in gelled products. Our invention involves the addition of sucrose-type polyols to polyepoxides so that the epoxy resin derivative is in the interior of the polyol or at the end of the polyol chain. The preparation of our products is more easily accomplished and is more reproducible than those of the prior art. Also, the functionalities of the initiators of this invention are higher than the triol used in the Japanese patent.
U.S. Pat. No. 3,012,984 describes how hydroxyl terminated polyesters, epoxy resins and isocyanate-terminated prepolymers may be reacted in an inert organic solvent to produce metal primers and coatings. U.S. Pat. No. 3,010,940 discloses how phenol, epoxy resins, polyisocyanates and alpha-methylbenzyldimethylamine react to produce various polyurethane coatings. U.S. Pat. No. 3,448,046 describes how polyols containing chlorine are mixed with epoxy resins before reaction with an isocyanate. The free epoxides scavenge the HCl in the polyol and do not contribute to the functionality of the polyol. The reaction of an epoxide with an alcoholic hydroxyl group is set out in U.S. Pat. No. 3,317,609. The production of amino alcohols by reacting aminoethoxyethanol with an epoxide is set out in U.S. Pat. No. 3,335,186. Further, British Pat. No. 968,102 describes how polyols suitable for polyurethane foams may be prepared from the reaction of a polyol, and an epoxy resin in the presence of an acidic catalyst.
Other prior art polyols include those described in German Offenlegungschrifft No. 2,056,080. This patent describes how epoxy adhesives may be made by the reaction of epoxy resins with 4-mercaptobutanol-blocked urethane prepolymers which are made from toluene diisocyanate and various polyols. German Offenlegungschrifft No. 1,905,696 discloses how polyurethane lattices may be produced by chain-extending a urethane prepolymer by using the reaction product of polyethylene glycols of a molecular weight of about 5,000 to 10,000, and an aromatic diglycidyl ether. The modification of epoxy resins by heating them with added polyalkoxylated disaccharides is described in Belgium Pat. No. 785,020.